The Effects of Different Treadmill Running Periods on Bone Mechanical Strength in Ovariectomized Mice / The Japanese Journal of Rehabilitation Medicine

ABSTRACT

This study investigated how different treadmill running periods effected bone mechanical strength in ovariectomized mice. Eighty female ICR mice aged 12-weeks-old were used. All mice were divided into 8 groups (<i>n</i>=10) randomly, and had either a sham-operation (<i>n</i>=10) or an ovariectomy (<i>n</i>=70). The SHAM group and one OVX group (NR) were used as non-running control groups, with the remainder comprising the treadmill running groups the LA (8 m/min), MA (16 m/min), and HA (24 m/min) groups which ran for 12 weeks, and the LB (8 m/min), MB (16 m/min), HB (24 m/min) groups which ran for 6 weeks for 25 min on 5 days/week. After this experiment, maximum loads for the femur and tibia were measured by three-pointed bending test, and the bone mechanical strength of the bones was calculated. Also, the dry bone weight and ash content of the bones were measured. Maximum femur and tibia load and bone mechanical strength were affected by running speed and term significantly. Maximum load and bone mechanical strength of tibia were shown as an interaction. Bone mechanical strength in all running groups was higher than that in the NR group, significantly. This study suggested that treadmill running prevented a reduction of bone mechanical strength, and that treadmill running was most effective in the LA and MA groups (running at low and medium speed and for a long period).